problem with power : q^2 power(q,2) q**2

GAMS
1

Hi every body
I have one of this three Equation
It is a MINLP program


Pow_ps_g(L,t) (ord(t) GT 1).. P_ps_g(L,t) =e= (-1.03036*Ig(L,t)+259.33 * Qg_ps(L,t)- 0.000145* Qg_ps(L,t)*Qg_ps(L,t))/1000000; or Pow_ps_g(L,t) (ord(t) GT 1)… P_ps_g(L,t) =e= (-1.03036Ig(L,t)+259.33 * Qg_ps(L,t)- 0.000145 (Qg_ps(L,t)**2))/1000000;
or
Pow_ps_g(L,t) $(ord(t) GT 1)… P_ps_g(L,t) =e= (-1.03036Ig(L,t)+259.33 * Qg_ps(L,t)- 0.000145 power (Qg_ps(L,t),2))/1000000;



Qg_ps is a variable than can vary between 200 upto 357.5
Qg_ps can also be equal to 0 if Ig(L,t) =0


but when I see the solve summery I see that the the powered part of my equation is not accounted like this

Pow_ps_g(1,2)… P_ps_g(1,2) - (0.00025933)Qg_ps(1,2) + 1.03036E-6Ig(1,2) =E= 0 ; (LHS = 0)



why???

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2

Gams write down the linearized version of the equation.

Cheers

Renger



From: gamsworld@googlegroups.com [mailto:gamsworld@googlegroups.com] On Behalf Of ja Mor
Sent: Montag, 11. Mai 2015 09:29
To: gamsworld@googlegroups.com
Subject: problem with power : q^2 power(q,2) q**2



Hi every body

I have one of this three Equation

It is a MINLP program





Pow_ps_g(L,t) $(ord(t) GT 1)… P_ps_g(L,t) =e= (-1.03036Ig(L,t)+259.33 * Qg_ps(L,t)- 0.000145 Qg_ps(L,t)*Qg_ps(L,t))/1000000;

or

Pow_ps_g(L,t) $(ord(t) GT 1)… P_ps_g(L,t) =e= (-1.03036Ig(L,t)+259.33 * Qg_ps(L,t)- 0.000145 (Qg_ps(L,t)**2))/1000000;

or

Pow_ps_g(L,t) $(ord(t) GT 1)… P_ps_g(L,t) =e= (-1.03036Ig(L,t)+259.33 * Qg_ps(L,t)- 0.000145 power (Qg_ps(L,t),2))/1000000;







Qg_ps is a variable than can vary between 200 upto 357.5

Qg_ps can also be equal to 0 if Ig(L,t) =0





but when I see the solve summery I see that the the powered part of my equation is not accounted like this



Pow_ps_g(1,2)… P_ps_g(1,2) - (0.00025933)Qg_ps(1,2) + 1.03036E-6Ig(1,2) =E= 0 ; (LHS = 0)







why???




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3

thanks Renger van Nieuwkoop
can you explain more_? I cant understand you . what is the solution?

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4

Gams writes your equations in the linearized form and puts in the starting values (if given, otherwise zero) for your variables.

This is just a diagnostic tool and of no relevance for the actual solving procedure.

For example, if you have an equation x =G= 2, this will appear in your output something like 0 -2 > 0, infeasibility -2. If you would have put a starting value for x of 3, you would get 1 > 0 and no infeasibility.

This might be helpful if you are testing a model which should depict an actual situation and you want to do counterfactuals. For example, demand =E= supply is one equation and you know prices, quantities and demand and supply functions in your “benchmark” scenario, you could give Gams these starting values for the variables. Gams would fill in those values, and if your model is correct, would have a solution equal to the starting values (if you set iteration limit to zero, Gams finds the solution without having to iterate). If you made a mistake in your supply equation, you would get in your equation listing an infeasibility for that equation, and you now have information on which equation is wrong.

If you corrected this, you could introduce a tax and solve the model and get new values you can compare to the benchmark values.

Hope this helps

Renger



From: gamsworld@googlegroups.com [mailto:gamsworld@googlegroups.com] On Behalf Of ja Mor
Sent: Montag, 11. Mai 2015 11:01
To: gamsworld@googlegroups.com
Subject: Re: problem with power : q^2 power(q,2) q**2



thanks Renger van Nieuwkoop

can you explain more_? I cant understand you . what is the solution?


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